The Merchant Navy pacifics: innovation ahead of their time

Article by first written by Ian Crowder in 2005 and updated 2017 and August 2019


Picture: 35006 in Southern Railway Malachite Green livery at Exmouth Junction shed shortly after nationalisation, in 1949. 'British Railways' has replaced 'Southern' on the tender side while the locomotive number has changed from 21C6.  The 'Southern' roundel on the smokebox door has been replaced with a standard BR numberplate. (Picture P&O Society collection, photographer unknown)


After a long and meticulous overhaul at Toddington on the Gloucestershire Warwickshire Railway, Merchant Navy class pacific 35006 Peninsular & Oriental SN Co - or 'P&O' for short - entered revenue-earning service once again on 16 May 2016.  


At its triumphant public debut, the engine promptly showed what it is capable of, handling two return trips to Cheltenham hauling a 14-coach train with consummate ease.


Trains of such length were of course, the 'bread and butter' for these powerful class 8 locomotives - among the most powerful express steam locomotives to operate in Britain. Of course, members of this class never visited the Stratford-upon-Avon to Cheltenham line - their 'patch' was on the Southern routes from Waterloo to Bournemouth and to the West Country. 


However, another member of the class - restored no. 35028 Clan Line - did run through Toddington in a positioning move from the Midlands to Bristol in 1976, just before the line was closed by British Rail, while in 2005 and 2006, sister Merchant Navy no. 35005 Canadian Pacific spent some time on the line with two separate visits to the Cotswolds. It was without a doubt, an inspriation to the 'P&O restoration team.


'Space age' technology for the Southern

35006 at Salisbury, its home base, in 1959 just before being taken into the works to lose its air smoothed casing during rebuild (Photo John Lewis)

35006 coasts home towards Warterloo through Winbledon with an Up West of England express in 1963 (Photo P&O Society collection)

Spot any differences?: an almost identical angle to the above taken 53 years later, this time accelerating away from Gotherington on 8 July 2016 (Photo: Malcolm Ranieri)
Ta-Da! Pete Waterman dedicates 'Peninsular & Oriental SN Co' at Toddington on 16 May 2016 (Photo: Ian Crowder)
''P&O' dressed for the celebration of the merchant Navy on 3rd September 2019, on shed at Toddington (Photo: Ian Crowder)

'P&O' - big and impressive as it is, it was not however, built in the form we see it today.


In fact, it's hard to imagine how people might have reacted when they saw the first member of the class emerge from Eastleigh works in 1941, at a time of wartime austerity.


'Sensation' is probably an understatement - the locomotives were anything but conventional in appearance and engineering innovation. They sported a futuristic, sleek, 'air-smoothed' design quite unlike anything that had appeared on the Southern Railway before.


The Southern Railway's Chief Mechanical Engineer, O V S Bulleid, came from the London & North Eastern Railway which of course had already produced the streamlined 'A4' pacifics (of which world speed record breaker Mallard is a member) and although influenced by LNER practice, was arguably far ahead of his time.


Three batches of 10 were completed, the last being delivered by British Railways following nationalisation.


The 30 Merchant Navy's were a three-cylinder design with a boiler featuring a wide firebox - but that's about as far as LNER comparisons go. Behind the unconventional 'air-smoothed' casing (possibly influenced by Gresley's semi-streamlined P2 class 2-8-2's) and American 'Boxpok' style wheels were a host of ideas never tried before. Not least of these was chain driven valve gear between the frames, the valve gear and middle motion being totally enclosed in an oil bath, intended to eliminate the need for staff to get between the frames to 'oil up'.


A steam reverser operated the valve gear and the whole assembly completely eliminated the 'hammer-blow' on the track associated with conventional locomotives. Another major innovation included an all-steel boiler equipped with thermic siphons within the firebox to promote better water circulation. The workinbg pressure of the boiler was an unprecedented 280lb/ Rocking grate and hopper ashpan made for quick and easy disposal while the cab layout was ergonomically designed to simplify operation, this including steam-operated firehole doors worked by a treadle. An electric generator powered lighting for cab, gauges, inspection lights and head and tail train lights.


The decision was taken to name the class after shipping companies serving the Southern Railway's docks and also to recognise the huge sacrifice made by Britain's merchant fleet and seamen in conflicts particularly the Second World War.  It was an inspired choice that not only touched on a poignant subject as so many seament lost their lives but also highlighted the SR's connections with the continent and international travel - even if it meant some extremely long names (such as 35006: Peninsular & Oriental Steam Navigation Co!).


Interestingly, of the 30 names chosen for the class, only two remain today as marketing names - P&O and Cunard.


Change for the better?

Although the Merchant Navy class (and the similar but smaller West country and Battle of Britain classes) proved to be fast, free running and powerful they were beset with a host of irksome maintenance problems. For example, the oil bath proved impossible to keep oil tight; the chains were prone to stretching and wear which affected valve timing and the steam reverser could be difficult to set accurately. The air-smoothed casing, while easy to keep clean (the engines were designed to go through carriage washers) proved a nightmare for access when things went wrong. They spent much more time in the works than they should.


However, the boiler was a triumph - it was free steaming and, if a little heavy on coal, would deliver whatever the driver demanded of it - provided the fireman could keep up! The class routinely ran at speeds well in excess of 80mph, 100mph not being uncommon.


In 1955, the British Railways Board gave authority for the first 15 members of the class to be rebuilt to more conventional design in order to reduce the maintenance issues and the first, no. 35018, emerged later that year. The influence of R A Riddles (designer of the British Railways standard designs) was clear in the rebuild directed by R G Jarvis: and an obvious comparison was made with the BR 'Britannia' pacifics.


Gone was the air-smoothed casing and chain driven valve gear, replaced with three separate sets of Walschearts gear. Gone too, was the troublesome steam reverser. A new smokebox was fitted (but retaining the distinctive oval Bullied smokebox door); and an additional smokebox saddle fitted to strengthen the frames. A new superheater feeder and outside steam pipes were provided along with new pistons, piston rods and cylinder drain cocks. New mechanical lubricators were fitted, along with a new regulator and ashpan design. Finally, weights had to be fitted to the wheels to counteract the hammer-blow effect produced by the conventional motion.


Success of the rebuild was such that all members of the class were rebuilt by 1959 and similar work immediately started on the 110 light pacifics (although not all of those were rebuilt).


Although the rebuilt locomotives were expected to remain in service until 1987, the modernisation plan put paid to that - and like Riddles' Standard classes, had lamentably short lives. Nevertheless, the Merchant Navy's put in commendable and reliable performance with little, if any, loss in performance in their new form. Indeed, there are several authenticated examples of the rebuilt locomotive exceeding the magic 'ton' - no. 35003 Royal Mail topping 106mph with a Weymouth-Waterloo service between Basingstoke and Woking, just days before the end of SR steam in 1967.


The SR was the last main line in the UK to operate express services with steam: the Waterloo - Southampton - Bournemouth - Weymouth expresses remaining almost exclusively Bulleid-pacific hauled right to the end. Appropriately, it fell to the last member of the Merchant Navy class, 35030 Elder-Dempster Lines to haul the very last steam-hauled train to Waterloo: the 14.11 Weymouth-Waterloo on 9 July 1967. The next day, modern traction took over and there was not a breath of steam left to be seen. A sad day indeed and seemingly, the last rites of a remarkable class of locomotive had been performed.


Fortunately, 11 members of the Merchant Navies (just over a third of the total!) survived the cutter's torch.  35028 was bought privately straight out of BR service and has for example, over many years put in sterling and reliable performances on tour duty, particularly with the Belmond British Pullman (previously VSOE) out of London Victoria.


Other members of the class have been restored or are close to completion after long and expensive restorations, while there is a project to return 35011 Genral Steam Navigation to its original 'unrebuilt' condition.


'P&O' returns triumphant

This fine locomotive finally entered service in May 2016 after an extremely painstaking restoration that started after its arrival at Toddington in 1983.  It was the second locomotive to be delivered from Barry Scrapyard in South Wales (the first was GW 2-8-0 no. 2807) to the embryonic Gloucestershire Warwickshire Railway's site on what remained of the yard and station.


On arrival it looked extremely forlorn - it was tenderless and anything easily removable had been stripped from it.  The meticulous attention to detail in the restoration, including construction of a brand-new tender, is evident - it is a fine, powerful locomotive that has become a significant attraction in its own right at the railway.


35006 was completed at Eastleigh works in 1941and originally numbered 21C6 in the SR's eccentric numbering system.  It was one of two members of the class which were fitted with asbestos board (rather than steel) air-smoothed casing.


The engine spent its entire working life based at Salisbury depot (72B) and was one of the final two (along with 35028) to be rebuilt in 1959 into the form that you see it today. It was a familiar sight on the heavy West of England expresses including the 'ACE' - the Atlantic Coast Express - to Devon and Cornwall.  The engine was withdrawn in August 1964 having clocked up more than 1.1 million miles in its Southern Railway and British Railways service.  Sold to Woodham Bros at Barry in South Wales for scrap, it was rescued by the present owners, the 'P&O' Locomotive Preservation Society in 1983 and moved to Toddington.


It moved under its own steam for the first time in August 2015, albeit with only two of its three cylinders connected, more than half a century after its last fire was dropped.


The engine's re-entry into public service was a tremendous day in May 2016 and the engine has performed with only relatively minor teething issues since then and is settling down to be a reliable and popular performer.


Indeed, the engine - appropriately, considering that it is of the Merchant Navy class - could be perhaps be regarded the 'flagship' of the Gloucestershire Warwickshire Railway's operational fleet!


UPDATE: On Tuesday 3rd September the GWSR celebrated the centenary of King George V bestowing on Britain's merchant shipping fleet the term: 'Merchant Navy'.  After a short act of remembrance at 09.30 no. 35006 'P&O' headed the 10.00 train from Toddington to Cheltenham and carried a special headboard and the Red Ensign on the buffer beam and smoke deflectors for the rest of the day You can read the full story here and you can view images here